Calcium Confidential: Secret Food Sources of Calcium
Photographs of well-known celebs and athletes with milk mustaches are one way the milk industry encourages calcium-deficient Americans to beef up their intake by drinking three glasses of milk per day. Why? Calcium is the mineral most critical to achieving and maintaining strong, healthy bones and minimizing bone loss later in life, and milk and other dairy products are often promoted as the preferred source. It makes sense. Nutrient-dense dairy products contain high concentrations of calcium: one 8-ounce glass of milk provides 256 milligrams of calcium, which is about one-fourth of the recommended daily intake. (Click here for more nutrient benefits of calcium.)
But if you're lactose-intolerant, a vegan and don't eat dairy products, or simply want calcium options from sources other than dairy, there are other ways to get this important mineral. Studies show that you can maintain bone health with a diet in which calcium is obtained from non-dairy sources.
According to the U.S. Department of Agriculture, the calcium absorption from most foods, including dairy products and grains, is about the same. However, calcium may be more poorly absorbed from foods high in oxalic acid (spinach, sweet potatoes, and beans) or phytic acid (unleavened bread, raw beans, seeds, and nuts). These acids bind with calcium and prevent its absorption, but they don't prevent the absorption of calcium from other foods eaten at the same time. There are many plant-based sources that are well absorbed, such as soybeans , soynuts, bok choy, broccoli, collards, Chinese cabbage, kale, mustard greens, and okra. (Click here for more food sources of calcium.)
But vegetables alone may not be enough because the amount required to reach the adequate daily intake of 1,000 milligrams per day for adults (1,200mg for those 51 and older) set by the Institute of Medicine is not always practical for most Americans. The key is to combine vegetable sources with other non-dairy calcium-rich foods such as tofu made with calcium sulfate and calcium-fortified soymilk and juices. Be sure to look carefully at the nutrition label to verify that the tofu you are buying is made with calcium sulfate. Nigari (magnesium chloride) is another common coagulating agent used to make tofu but its calcium content is lower. (Click here for tofu recipes.)
You can also take calcium supplements to ensure that you're getting the recommended daily amount, but don't exceed 2,500 milligrams per day from both food and supplements. Excess intake can increase risk for some health problems like kidney stones.